This invention relates, in general, to semiconductor devices, and more particularly to a method of forming planar isolation regions in semiconductor structures.
Presently, there are many methods of forming isolation regions in semiconductor structures. However, there are many shortcomings and disadvantages associated with conventional methods. For example, conventional recessed oxide isolation generally has a non-vertical isolation angle that is associated with increased oxide encroachment into the active device region. Further, conventional recessed oxide isolation methods generally have a large process variance.
U.S. Pat. No. 4,526,631 entitled "Method for Forming a Void Free Isolation Pattern Utilizing Etch and Refill Techniques" issued to Silvestri et al. on Jul. 2, 1985, discloses a prior art isolation technique. Following the etching of a trench, a first insulating layer is formed on the sidewalls of the trench. The trench is then partially filled with an epitaxial silicon. Since the top surface of the epitaxial silicon is faceted, a capping second insulating layer is used to fill the remainder of the trench and also to cover an area above the trench. Following the formation of the capping second insulating layer, a planarization etch back is performed.
Another prior art isolation region method is disclosed by Yu and Witkowski in an article entitled "New Bird's Beak-Free Device Isolation Technology", J. Electro-Chem. Soc.: Solid-State Science and Technology, October 1988, pages 2562-2566. Following the etching of a trench, hitride layers are formed on the sidewalls. Following this formation, a selective epitaxial silicon layer is grown in the field regions and is completely converted to thermal silicon dioxide film to form the field oxide. This disclosure claims the advantages of a uniform field oxide, no birds beak encroachment and no dislocations in active device areas. However, there are various process control issues associated with this disclosed method which make results hard to reproduce and also, the resulting isolation regions are nonplanar.